This blog discusses current weather, weather prediction, climate issues, and other topics

Monday, July 17, 2017

Melt Out at Paradise on Mount Rainier

Yesterday, July 16th was melt-out day at the official snow measuring site at Mount Rainier.

Located at roughly 5500 ft, this melt-out day is about 1 week later than typical for the past 100 years (information from Mark Albright, UW Research Scientist). Here is an interesting table showing the mean melt-out dates by decade at Paradise Mt Rainier:

Decade Date No. of Years----------------------1910s 16 July 2*1920s 10 July 9**1930s 3 July 101940s 1 July 101950s 17 July 9** 1960s 5 July 101970s 21 July 101980s 10 July 101990s 15 July 102000s 10 July 102010s 1​6 July 8***

* 1917 and 1918, ** 1925 missing, 1950 missing, *** 2010-2017

As you can see, there is no real trend towards earlier melt-out, which would be a sign of global warming. That will come, but later in the century.

What about a much lower site? Such as Stevens Pass (about 4000 ft above sea level)

The snowpack melted out this year on 7 June 2017 at the Stevens Pass SNOTEL site, with the melt-out this year tied for ​11th ​latest out of the past 37 years (the length of record there).

Mean melt-out dates by decade showing a trend towards later melt-out of the snowpack in recent years:

1980s: 30 May 1990s: 1 June 2000s: 2 June 2010s: ​4 June (thru 2017)

Similar to Paradise, the snowpack is holding on later into the warm season.

The maintenance of our snowpack into the summer helps maintain our streamflow into the summer, which is good for fish and water resources. By the middle of the century we expect the situation to change as warming causes more of our precipitation to fall as rain in the mountains.​

17 comments:

The date of melt out must be more than a function of temperature only. Snowfall and monthly temperature variations surely play a part. NOAA's climate date for Washington climate division 5 (Cascade Mountains west) seem to show close to 1 deg. F. average temperature increase beginning in the mid-1980's.

Similar to Eprman's comment, I'm wondering if this slightly later melt-out is more a function of increased middle to late spring precipitation in the form of snow? My climbing ranger friends on Mt. Rainier tell me that apex snowpack at 10,000 feet doesn't form until the middle to end of May. From what I understand, global warming is associated with an increase in springtime precipitation in the Pacific Northwest, and as the planet heats up significantly more towards the end of the century, our springs will become cloudier and rainier? So I might hypothesize here, that warming has started this trend, but that for now, we're still cool enough for that increased precipitation to come in as snow at alpine and sub-alpine elevations?

Cliff, my other question for you:

North Cascades Glaciers, as well as volcano glaciers, have all decreased in volume by approximately 30% over the past half century. This is highlighted in the data here:

http://www.nichols.edu/departments/Glacier/

So my question for you Cliff, is if we are still maintaining our winter snowpack average for the past century, what is the primary driver / forcing for glacier retreat and thinning? I personally have documented a ~900 foot retreat of the Roosevelt Glacier on Mt. Baker since 2001, and have noted significant thinning of the glacier, even at high elevations on the Glacier's accumulation zone. Rock outcroppings that were never present, are now sticking tens of feet above the ice, where glacier ice persisted as recently as 2007. It would appear that decreased winter snowpack is currently NOT the driving force for this. My hypothesis is that our summers have increased in overall heat intensity, and heat duration, however, I don't have data to support this.

Can you say anything about what is driving glacier retreat and thinning, despite current maintenance of our winter snowpack?

Thanks for that question, Russell. As an avid winter and summer skier based in Terrace B.C., the atrophy of our local glaciers is a concern as well. Our go-to 'summer ski' area received well below average snowfall in the accumulation season this year and this resulted in a well below average snowpack depth on the glacier. However, persistently cool cloudy conditions up to now have dramatically reduced the amount of snowmelt at treeline and alpine in north quadrant terrain. This has resulted in the snowpack depth creeping back up to about average above treeline and in the alpine terrain...in fact, almost all precip events up to now been falling as snow at the highest elevations and this has resulted in a relatively low net loss of snowpack depth at specific high elevation test areas in this zone. Visual observations of local higher elevation glaicers show that crevasses are unusually, robustly filled/bridged and the snowpack in the accumulation zones is healthy...

Like you, I suspect that summer season conditions are the main variables influencing glacier retreat and thinning. Beyond the obvious extreme snow winters where the sheer volume of snowfall and snowpack depth buffer the glacier ice even in long, warm, sunny summers, it would stand to reason that a cool, cloudy, relatively low precip summer is the best bet for glacier sustenance and resistance to thinning, melting and retreating.

Russell, if you had dug a little deeper into the source that you cited in reference to your claim about the trend in volume of North Cascades glaciers you would find probably a better answer than Cliff could supply you with. See the section on mass balance forecasting: http://www.nichols.edu/departments/Glacier/mass%20balance%20forecasting.htm and keep in mind that climate varies on annual as well as decadal timescales. Also, to be clear, it is not known whether all glaciers found in Washington's Cascades (including High Cascades) have decreased in volume over any particular period of time because not all of them are being monitored.

I was going to ask Russell's questions with less colorful anecdotes - very curious about glaciers as well as about what's happening at 3,000 feet. The lower you go, the more surface area there is for snowpack to accumulate; changes below 4,000 feet could take a big toll on summer streamflows and salmon.

I really appreciate you sharing the meltout data for these two stations. It would be interesting to see the results for even more stations.

How do we reconcile the apparent non-trend for these two stations with published research documenting observed shifts in runoff timing for much of the Western US? There are basins and rivers which are exceptions to the trend -- maybe these two are among them -- but the dominant story seems to be that the earlier-runoff shift is well underway -- not merely yet to come. See, e.g., http://journals.ametsoc.org/doi/pdf/10.1175/2011JHM1360.1

I have read the section on mass balance, and have read their published studies. It would appear that hotter summers are more than likely the driving force. However, I am curious about this from Cliff's meteorological point of view. He more than likely has far more data on the specific details about summer weather and climatic patterns over the past 30 years than do the Nichols College guys.

You mentioned:

" Also, to be clear, it is not known whether all glaciers found in Washington's Cascades (including High Cascades) have decreased in volume over any particular period of time because not all of them are being monitored."

There is actually very clear evidence that essentially every glacier in the cascade range (with the exception of Crater Glacier on Saint Helens) has been in a state of rapid retreat since the early 1980's. The Emmons Glacier on Rainier advanced for a bit during the 1990's because of a massive rockfall off of Little Tahoma that insulated the ice. The kinematic wave generated by that even has since run its course to the terminus of the glacier, and it has since resumed it retreat. In fact, the lower Emmons is now in a state of rapid collapse. While its true that ongoing studies are not happening on every single glacier, there are many studies happening, and there is not a single mention of glacier advance between North Cascades NP and Mt. Shasta (again, excluding the rapid advance of Crater Glacier). There's also very clear anecdotal evidence for widespread glacier retreat and high elevation thinning from the skiing and climbing communities. The Hummel twins, for example, have documented dramatic changes on every single glacier on Mt. Adams since the early 90's.

Well Cliff maybe. We have already warmed about 0.8C from 1880 and it appears melt out is not changing. How can that be? Unless we really have a more sensitive climate than the last 60 years of good data indicate, the changes will be quite manageable. There is a lot of scare mongering out there and special interest of all political stripes use fear as their best weapon to get what they want. Green groups are among the worst because educated society tends to believe them. Their track record is terrible.

Some of Organic Farmer's thoughts resonate with my own, and I also try to be very open to climate change indicators and research. But this isn't just an issue with climate change. It seems to be a much more challenging aspect of human nature. If we can't nail down the probability of an event, if the science isn't iron-clad, then even when the potential outcomes are devastating, we don't act.

Examples abound.

Nuclear weapons -- given numerous close calls and aging, fallible systems (ignoring intent), with city-killing thermonukes cocked and aimed on hair-triggers at most cities in the developed world, we either do nothing or build more or better ones. At risk: billions of lives

Antibiotic resistance -- we watch the changes, rapid as they are, and assume some drug company is going to save us. We don't make fundamental changes in how we use them nor do we make massive investments to mediate the risk. At risk: billions of lives

Unless the sword is visibly hanging directly over our heads where everyone can see and touch it, we talk but do very little. In that way, we don't differ that much from other animals. Whoever is unlucky enough to live when the bad times come will just have to persevere. Just like it's always been.

Cliff, I agree with you call against alarmism and I enjoy the intellectual skepticism.

But how can we use the single (well dual I guess) data points of melt-out at a certain elevation when measured against the noted decades long recession of some of our region's largest glaciers? (notable the Nisqually which extended far below paradise decades ago).

Also, the formation and collapse of ice caves across the region(paradise, mt hood, big four are almost gone, right?)

Glaciers in the Cascades, glaciers in Alaska, glaciers in Glacier Nat'l Park...most have been retreating since they reached maximum extent during the Little Ice Age. Nisqually glacier reached its maximum extent around 1840.

Ice around Glacier Nat'l Park may have been a mile thick 18,000 years ago, but the remaining glaciers are not left over from the Pleistocene. There is evidence the current glaciers formed within the last 6,000-8,000 years.

A couple other factors contributing to glacier retreat, that may be overlooked, are:

1. Some glaciers may still be trying to achieve a new post-LIA equilibrium (Little Ice Age). Put another way, they are still in retreat because it is taking them over a century to adjust to the post-LIA climate. This is less of a factor the further we get from the LIA and would affect mostly larger glaciers.

2. More importantly... over time, mean winter precipitation has shifted to earlier in the season. December was historically the wettest month in western WA but now the wettest month is November. With a higher proportion of precipitation falling earlier in the season before the snowpack builds, overall moisture content of the snowpack is reduced. I don't know to what extent this is supported by snowpack measurements but it makes sense in theory.